1. Field of the Invention
The present invention relates to a reflector plate to be suitably used in a reflection type display device and a reflection type display device comprising the reflector plate, and an electronic apparatus.
2. Description of the Background Art
In recent years, a reflection type display device for reflecting light incident from the outside and displaying a liquid crystal image without using a backlight has often been used in an electronic apparatus such as a personal computer, a television, a word processor, a cell phone or a portable information terminal in order to miniaturize, save a power and cut down cost. Since the backlight is not used in such a reflection type display device, it is important that the light incident from the outside is to be efficiently utilized to form an image.
For a reflection type display device of this type, conventionally, there has been known a structure shown in FIG. 1, for example.
The reflection type display device has such a schematic structure that a liquid crystal layer 215 is enclosed between an upper substrate 216 formed by a translucent material and a lower substrate 212 provided with a thin film transistor 214. There is provided a reflector plate 201 for reflecting light incident from the upper substrate 216 side.
The reflector plate 201 is provided between the upper substrate 216 and the lower substrate 212 as shown in FIG. 1A or provided on the back side of the lower substrate 212 as shown in FIG. 1B.
As shown in FIG. 2A, a structure of the reflector plate 201 has been proposed in which a plurality of reflecting units 210 provided with concave or convex reflecting planes having almost identical configurations to each other are arranged. Each of the reflecting units 210 is provided to have an irregularity such that an arrangement interval between the adjacent reflecting units is not completely identical. However, a variation in the arrangement interval is restricted to a constant range because of a structure in which the reflecting planes having almost identical configurations are arranged. Accordingly, the arrangement interval has a constant distribution setting an average arrangement interval to be a center as shown in FIG. 2B and acts as a reflecting diffraction grating including concavo-convex patterns having almost equal intervals if seen as a whole.
According to this structure, the incident light is scattered and reflected through each reflecting unit 210. Consequently, it is possible to prevent a deterioration in a visibility caused by the overlap of the direction of light reflected by the surface of the upper substrate 216 and that of light reflected by the reflector plate 201, and furthermore, to realize a wide angle of field.
However, there is a problem in that great coloring is caused by interference in the reflector plate 201 having the reflecting units 210, resulting in a deterioration in a visibility as described above.
FIG. 3 shows a diffracted light distribution in a Fraunhofer region of the concavo-convex pattern of the conventional reflector plate 201. It is apparent that a cyclic maximum value (peak) such as first-order light or second-order light in addition to zero-order light appears on diffracted light (zero-order light, first-order light, . . . , n-order light on diffracted light distribution in the Fraunhofer region will be hereafter referred to as zero-order diffracted light, first-order diffracted light, . . . , n-order diffracted light, respectively).
As a result of the investigations of the present inventors, it was found that the coloring caused by the interference is observed when a difference between the intensity of the first-order diffracted light and that of diffracted light at a peripheral angle is large.